In an article entitled "Detection, Repair and Prevention of Gas Leaks," published in the American Gas Journal, August 1959, pages 16-28, it is indicated that the amount of fuel gas lost from pipelines through leakage represents a great economic burden as well as a potential safety hazard. In addition, leakage of fuel gas reduces the effective capacity of a gas distribution system. Another adverse effect of leakage is a reduction in the level of pressure in the distribution mains below desirable limits.
In U.S. Pat. No. 3,507,725 to Hylak et al, there is disclosed a method of repairing gas main fibrous packed joints with a liquid sealing material which may be a liquid monomer such as styrene monomer, by introducing the monomer into the gas main in liquid form, and permitting it to flow to a low point in the system where a leaking joint exists, the packing of which becomes saturated with the sealant which then polymerizes over a relatively long period of time, namely six weeks to three months. Styrene is employed as a liquid, and no specific catalyst is named in the patent.
The U.S. Pat. No. 3,578,479 to Packo discloses sealing leaks in a vessel and the like with a sealant agent which is either a silicon hydride, a boron hydride or an alkoxide borane, together preferably with a metal alkyl. To achieve best results from the disclosed components, this system requires the use of the metal alkyl, a dangerously pyrophoric material, as a catalyst and or a co-reactant. Moreover, such metal alkyls have a poor shelf life and are easily subject to contamination. The seal produced by the co-reaction has a tendency to be brittle and lacks consistency and homogeneity due to stratifications which inevitably occur in the mixtures and differences in volatility curves in the components which give different relative concentrations at different temperatures.
Likewise, U.S. Pat. No. 3,608,000 to Anderson discloses the introduction into a vessel of sealants which are mixtures of volatile organosilanes such as dimethyl diethoxy silane, trimethyl ethoxy silane, propyl trimethoxy silane and diisopropoxy dimethoxy silane; and metal alkyls which react chemically to form solid products in accordance with the equations set forth at column 2, lines 4-5 of the patent. These systems, which require the same metal alkyl catalyst and or co-reactants as discussed above, suffer the same disadvantages.
The Bent et al U.S. Pat. No. 2,265,962 discusses in general the use of liquid silanes for sealing wells by reaction of the silane with water to form an insoluble shield or plug. Among the silanes mentioned are some alkoxy silanes, but no mercapto silanes and no aryloxysilanes are shown. In general the compounds disclosed are either too unstable or too low in volatility to be practical for use in gas phase sealing, or they would need to be used with other compounds in a manner not disclosed by the patentees. Similarly, U.S. Pat. No. 2,259,875 to Bent et al, a division of the aforementioned Bent et al patent, also relates to a process for treating leaks in the walls of gas boreholes using liquid silane compounds.
The Ceyzerial U.S. Pat. No. 3,580,939 discloses the use of aminosilanes as cross-linking agents for diorgano-polysiloxane compositions. These liquid compositions, which harden spontaneously in the presence of water, are suggested for joining slabs and pipes.
Anderson U.S. Pat. No. 4,026,976 shows the sealing of pipe leaks using a catalytically polymerizable volatile organic monomer, but this process undesirably shows the use of a catalyst such as a metal alkyl which consequently complicates the processing and increases the cost. Acrolein (acrylic aldehyde) catalyzed by NH.sub.3 is suggested, as is isoprene catalyzed by triethyl aluminum.
In addition to the Anderson patents mentioned above, a number of other prior patents show the use of volatile mixtures for pipe sealing. These include the Anderson U.S. Pat. Nos. 3,634,560; 3,711,305; 3,716,384; Packo 3,578,479 and Anderson 3,660,984. Also of interest in this regard is the Rossman U.S. Pat. No. 3,709,712 which relates to the use of volatile organic amines; and Packo U.S. Pat. No. 3,711,309 which relates to the use of volatile alcohol or glycol ethers. Of somewhat less interest are the U.S. Pat. Nos. to Anderson 3,483,736; 3,523,771; Packo 3,483,735; 3,572,085; and 3,361,547 which relate to the detection of gas leaks.
In spite of all the work which has been done in the field of gas phase sealing, as noted above, most sealing of gas containing pipe continues to be carried out by archaically attempting to locate the leak, then excavating at the believed site of the leak, followed by applying a physical patch to the leak. Dogs are still being trained to sniff out gas leaks, although flame ionization is often used; these are both expensive techniques, and very often are unable to pinpoint the leak site, as gas may leak from one point and travel along the pipe for a considerable distance before reaching the surface where it can be detected. Also excavation is not only expensive but is impractical in some cases as where gas lines pass beneath large buildings.
Significant sealing problems also continue to occur in other gas containing conduits as well. Both above-ground and underground telephone conduits cannot tolerate moisture, as moisture tends to impregnate the dielectric material separating the telephone wires with the results that cross-talk occurs between adjacent lines; this problem is presently controlled at great expense by constantly feeding dry gas, e.g. nitrogen under pressure, through the telephone conduit. Problems of gas leakage also occur in many other environments including chemical processing plants and air conditioning units with resultant difficulties, and wherein repair may be expensive and inconvenient.